Budburst phenology of sitka spruce and its relationship to white pine weevil attack

Phenology of budburst development of Sitka spruce, Picea sitchensis Bong. Carr., measured at two sites on Vancouver Island, British Columbia, Canada, was under strong genetic control, with family heritability (h(f)(2)) ranging from 0.45 to 1.0, depending on phenology stage. On average, families with resistance to the white pine weevil, Pissodes strobi (Peck), initiated and maintained a faster rate of bud development than families from susceptible parents, requiring lower heat accumulation to reach particular stages of bud development, However, a large overlap occurred, with one resistant family having a budburst phenology not significantly different from the susceptible families and some susceptible families having phenology as early as that of resistant families, It is postulated that resistance is a multicomponent trait based on different resistance mechanisms, some of which may be correlated with phenology but not others, Close observation of weevil behaviour through the season indicated that resistant families experienced reduced weevil presence, copulation and oviposition rate with respect to susceptible families. (C) 2000 Elsevier Science B.V. All rights reserved.